Piston Engine Systems Part 1 Flashcards
The two magneto ignition systems?
High and Low tension
Purpose of the distributor?
To lead the high voltage to the appropriate plug and fire in the correct sequence
The principle of the low tension magneto is the same as the high tension magneto in so far as how the principle current flow is induced. However, a low voltage is induced in the magneto and flows to the primary windings of a transformer near the spark-plug. It is within the -
transformer that this low voltage is stepped up to a high voltage and led to the plugs.
The advantages of the low tension magneto:
- Lighter due to the relatively lightweight leads from the magneto to the plugs due to less insulation required
- A relatively low weight ignition harness may be used.
- Less electrical leakage due to lower voltage
- Less radio interference or static occur
- Less trouble and more efficient
The type of magneto system(single or dual).
This type incorporate a self contained unit; that is, the magnet, coil, breaker assembly and distributor are all housed in what is called the “magneto”.
Single magneto system
The type of magneto system(singe or dual).
This magneto incorporates two magnetos in one housing where one rotating magnet and cam are common to two sets of breaker points and coils.
Dual magneto system
It is important to remember that the rotating magnet of the magneto system only produces an effective and strong spark once the magnet is rotating at a speed of about 500 rpm. Any speed below this value results in -
weaker sparks
What is this negative effect called:
low engine revolutions during the start procedure require a retarded, or later, spark to prevent this effect. This effect means that the ignition of the inlet gas, by the early spark produced by the normal advanced timing, can cause a premature power stroke.
Kick-back
Which type of starting aid.
This aid is a small induction coil to which battery voltage is applied and converted into high voltage before being fed to the distributor of the magneto, the rotor of which contains two electrodes.
It provides a retarded spark for easier starting at low RPM. This starting aid is only energised when the “start” position is engaged, and disengages once the start position has been released.
The booster coil
Which type of starting aid.
This aid is only energised during the time that the engine is started. This system feeds DC from the battery to the aid which converts the flow into a pulsating DC of about 200 pules per second before sending it to the left magneto via a set of breaker points. This system incorporates a magneto switch labelled off, left, right both and a spring loaded start position. When the start position is selected the right magneto is grounded which prevents a spark occurring at the normal timing. Once the magneto switch is set to both, this aid is de-activated.
The induction vibrator
Which type of starting aid:
This aid is usually incorporated in the left magneto. This magneto employs flyweights and a spring-loaded coupling which initially prevents the magneto from turning. Once the spring is fully wound it releases the magnet which, due to its now increased rotation, produces both a hot and late spark during the start. Once the engine is running, the centrifugal force of the flyweights keeps the aid disconnected. This type of system usually incorporates a magneto switch marked off, left, right and both with a separate starter button.
Impulse Coupling
The high voltage generated by the magnetos is carried to the spark plugs through the ignition leads. Efficient engine performance requires that this current be carried to the -
plugs without loss
Between a primary and secondary coil, voltage can be stepped up from the primary to the secondary by?
Increasing the windings of the secondary
